DataStream.cpp revision 263508 
1284345Ssjg//===--- llvm/Support/DataStream.cpp - Lazy streamed data -----------------===//
2284345Ssjg//
3284345Ssjg//                     The LLVM Compiler Infrastructure
4284345Ssjg//
5291563Sbdrewery// This file is distributed under the University of Illinois Open Source
6291563Sbdrewery// License. See LICENSE.TXT for details.
7291563Sbdrewery//
8284345Ssjg//===----------------------------------------------------------------------===//
9284345Ssjg//
10284345Ssjg// This file implements DataStreamer, which fetches bytes of Data from
11284345Ssjg// a stream source. It provides support for streaming (lazy reading) of
12284345Ssjg// bitcode. An example implementation of streaming from a file or stdin
13284345Ssjg// is included.
14284345Ssjg//
15//===----------------------------------------------------------------------===//
16
17#define DEBUG_TYPE "Data-stream"
18#include "llvm/Support/DataStream.h"
19#include "llvm/ADT/Statistic.h"
20#include "llvm/Support/FileSystem.h"
21#include "llvm/Support/Program.h"
22#include "llvm/Support/system_error.h"
23#include <cerrno>
24#include <cstdio>
25#include <string>
26#if !defined(_MSC_VER) && !defined(__MINGW32__)
27#include <unistd.h>
28#else
29#include <io.h>
30#endif
31using namespace llvm;
32
33// Interface goals:
34// * StreamableMemoryObject doesn't care about complexities like using
35//   threads/async callbacks to actually overlap download+compile
36// * Don't want to duplicate Data in memory
37// * Don't need to know total Data len in advance
38// Non-goals:
39// StreamableMemoryObject already has random access so this interface only does
40// in-order streaming (no arbitrary seeking, else we'd have to buffer all the
41// Data here in addition to MemoryObject).  This also means that if we want
42// to be able to to free Data, BitstreamBytes/BitcodeReader will implement it
43
44STATISTIC(NumStreamFetches, "Number of calls to Data stream fetch");
45
46namespace llvm {
47DataStreamer::~DataStreamer() {}
48}
49
50namespace {
51
52// Very simple stream backed by a file. Mostly useful for stdin and debugging;
53// actual file access is probably still best done with mmap.
54class DataFileStreamer : public DataStreamer {
55 int Fd;
56public:
57  DataFileStreamer() : Fd(0) {}
58  virtual ~DataFileStreamer() {
59    close(Fd);
60  }
61  virtual size_t GetBytes(unsigned char *buf, size_t len) LLVM_OVERRIDE {
62    NumStreamFetches++;
63    return read(Fd, buf, len);
64  }
65
66  error_code OpenFile(const std::string &Filename) {
67    if (Filename == "-") {
68      Fd = 0;
69      sys::ChangeStdinToBinary();
70      return error_code::success();
71    }
72
73    return sys::fs::openFileForRead(Filename, Fd);
74  }
75};
76
77}
78
79namespace llvm {
80DataStreamer *getDataFileStreamer(const std::string &Filename,
81                                  std::string *StrError) {
82  DataFileStreamer *s = new DataFileStreamer();
83  if (error_code e = s->OpenFile(Filename)) {
84    *StrError = std::string("Could not open ") + Filename + ": " +
85        e.message() + "\n";
86    return NULL;
87  }
88  return s;
89}
90
91}
92